1. Field of the Invention
The present invention relates to dry strength additives for paper and more particularly it relates to polyamidoamine/epichlorohydrin resins bearing polyol sidechains.
2. Description of the Prior Art
Strength is a very important property of paper products. At constant basis weight, the use of dry strength additives increases strength. Dry strength agents enable the papermaker to use less pulp, less expensive pulp and/or more filler while making sufficiently strong, stiff and opaque paper products. Benefits to the users of paper products include stronger packaging and lower shipping or postage costs. Conventional dry strength agents include starch, urea/formaldehyde resins, melamine/formaldehyde resins, acrylamide copolymers and polyamidoamine/epichlorohydrin resins.
U.S. Pat. No. 3,962,159 (Ray-Chaudhuri, et al.) discloses copolymerization of water dispersible starches, polyamidoamines and epichlorohydrin. The weight ratio of starch to polyamidoamine is between 1:9 and 9:1. While Ray-Chaudhuri uses the term "graft copolymer" in fact he is making block copolymers of the polyamidoamines and starch using epichlorohydrin as a condensing agent. All U.S. Pat. No. 3,962,159 preparations form carbon-oxygen bonds between the starch and the polyamidoamine except for the one in Example 19 where a quaternary ammonium bond is formed.
U.S. Pat. No. 3,314,897 (Gaertner) discloses treating polysaccharide substrates (starch, textiles, such as cotton, linen, rayon, and cellulose paper products) with a minor amount of a prepolymer composed of aliphatic amine/epichlorohydrin adduct reacted with an amine having at least 2 amino hydrogens. In other words Gaertner uses a minor amount of his prepolymer to modify the polysaccharide substrates instead of modifying a polyamidoamine/epichlorohydrin resin by including polyol sidechains and obtaining a water soluble product.
U.S. Pat. No. 3,320,066 (Garth) discloses the separate addition of polyamide-epichlorohydrin resin, dialdehyde carbohydrate and optionally carboxymethyl cellulose and/or cationic starch to paper pulp, i.e., to the dilute slurry of paper pulp obtained after the beating operation.
South African Patent 695018 discloses starch/polymeric polyamine compositions wherein the polyamine is formed by a reaction of an alkylene dihalide, e.g. ethylene dichloride, and an amine, e.g., diethylenetriamine. There is no disclosure of making a polyaminoamide or a polyaminoamide/epichlorohydrin resin.
French Patent 1,488,141 (which corresponds to Canadian patent 797,130) discloses improving the strength of cellulosic material by (a) treating an aqueous suspension of cellulose fibers with a cationic wet strength resin (such as cationic urea-formaldehyde resin, and cationic polyamides, obtained from the reaction of polyalkylenepolyamine and dicarboxylic acid which are crosslinked with epichlorohydrin) (b) adjusting the pH of the suspension to 4.0-5.5, (c) treating the suspension with a dialdehyde polysaccharide, (d) adjusting the pH of the suspension to 4.0-5.5 and (e) forming a web from the treated cellulose fibers.
U.S. Pat. No. 4,097,427 (Aitken) discloses the interaction of polyalkylenepolyamine/epichlorohydrin resins with starch for improved wet strength. It does not disclose polyamidoamine/epichlorohydrin resins.
U.S. Pat. No. 3,763,060 (Hamerstrand et al.) discloses the interaction of sodium starch xanthate with polyamide polyamine-epichlorohydrin (PAE) resin wherein the bond between the starch xanthate and the PAE resin is a carbon-sulphur bond.
U.S. Pat. No. 4,940,514 (Stange, et al.) discloses the interaction of vinyl polymers with enzymatically digested starch. There is no disclosure of polyamidoamine/epichlorohydrin resins.
U.S. Pat. No. 4,818,341 (Degen, et al.) discloses the interaction of vinyl polymers with enzymatically digested starch. There is no disclosure of polyamidoamine/epichlorohydrin resins.
U.S. Pat. No. 5,334,287 (Hartmann, et al.) discloses the use of N-vinylcarboxamide free radical graft copolymers of mono-, oligo- or poly-saccharides. It does not disclose polyamidoamine/epichlorohydrin resins.